MK co-creator, Ed Boon, realizes there is still a strong demand for more characters and has changed his tune a bit about more DLC characters:

Our original plan was to do four [characters]...

...you know, if it’s just this crazy, ridiculous success then we have to at least entertain the idea.

But despite the demand, Boon and team want to direct their attention to their next "games":

Obviously, we want to start the next games and whatnot.

Games? Does that mean that more than one MK game is in development? Possibly. But at this point I'd still like a few more DLC characters for the Mortal Kombat I'm playing now rather than having to wait a year or longer for another installment. I've waited long enough for a real MK, dammit!